He only forgot to mention one little thing:
Imagine, you have multiple python apps on your server. Some need version 1 of library FooBar, some need version 2 of it.
How could you install 2 different versions of one library on the same machine?
Or another scenario, you don't want to install it as root.
You are just a normal user, without root/admin privileges and need to install that library.
Virtualenv steps in here.
You basically create a new path for your application, where python and all libraries will be installed.
This section covers Python Version 3.3+.
Go into your directory, where your application will be.
On Linux enter:
python3 -m venv ENV_DIR
On Windows enter:
C:\Python36\python.exe -m venv ENV_DIR
python3 and C:\Python36\python.exe are your Python executables. This differs from Python version to Python version.
ENV_DIR is a non existing folder, that will be created, I usually use env as name, but this is up to you.
Go to your application folder.
On Linux:
$ source env/bin/activate
On Windows:
$ env\Scripts\activate
And your command line will now look like that:
(env)$
Now you can pip install all the things you want.
Oh, and you exit this environment like that:
(env)$ deactivate
You want to get rid of that environment?
$ rm -rf env
On Windows, you just delete the env folder
Did you know, that you can make some profit with your witness vote?
Also sorry for the blatant image copy;)
